An embroiderable sewing machine is equipped with different types of embroidery frames having various sizes of sewable areas. The user is allowed to select an embroidery frame having a sewable area most suitable for the embroidery pattern to be sewn from the given embroidery frames and attach the selected embroidery frame to an embroidery unit of the sewing machine. Such configuration requires the sewing machine to detect the size of the embroidery frame attached in order to control embroidering of the desired embroidery pattern.
Digital and analog detection systems are generally known for frame-type detection of the embroidery frame attached to the sewing machine.
Under the digital system, the embroidery frame is provided with bumps that are arranged in a combination specific to each embroidery frame, whereas the embroidery unit is provided with a plurality of detections switches constituting a detection sensor allowing detection of the bumps. Under such configuration, the type of embroidery frame attached to the embroidery unit is detected by the combination of the detection signals outputted from each of the detection switches.
Under the analog system, the embroidery frame is provided with bumps, whereas the embroidery unit is provided with a voltage output element that outputs voltage signals of various magnitudes depending on the bumps detected. Under such configuration, the type of embroidery frame attached to the embroidery unit is detected by the magnitude of voltage signal outputted by the voltage output element.
For instance, an embroidery sewing machine described in pages 3 and FIGS. 1 and 5 of JP 2004-254987 A is provided with an X-directional carriage movable in the X-direction and having holder body connected to it. The holder body has left and right arms, the right arm being secured to the right end of the holder body and the left arm provided slidably on the left end of the holder body to serve as a movable holder. Further, the movable holder has a detection subject attached to its underside. The detection subject comprises a plurality of detection subject sections aligned in series along the lengthwise direction of the movable holder to exhibit a generally stepped configuration. The holder body is provided with a detector comprising a potentiometer that outputs voltage signals associated with the height of the detection subject sections.
When the user secures the embroidery frame to be used on the lateral arms of the holder body after laterally positioning the movable holder suitable for the size of the embroidery frame, a detection arm of the detector is rotated depending on the height of the detection subject section. Based on the voltage signal outputted from the detector depending on the height of the detection subject section, a controller provided on the sewing machine detects the type of embroidery frame attached to the carriage.
The latest sewing machines of this type have increasing number of frame types to facilitate embroidering of various embroidery patterns. The embroidery sewing machine described in the above described publication detects the embroidery frame type based on the size of the voltage signal outputted from the detector depending on the height of the detection subject section on which the detection arm contacts when the movable holder having the stepped detection subject is moved depending on the embroidery frame attached. In order to accurately distinguish the embroidery frame type by the difference in the voltage signal outputted from the detector, the voltage signals need to be outputted at predetermined intervals. In other words, the difference in height of the neighboring detection subject sections must take a predetermined amount or greater. Furthermore, maximum rotation amount of the detection arm of the potentiometer serving as the detector is approximately 180 degrees. The above described limitations of the embroidery sewing machine disclosed in the referenced publication only allows distinction of about 5 embroidery frame types, and thus cannot distinguish large number of frame types in the magnitude of 10 to 15 types, for example.
Contrastingly, under the digital system where embroidery frame types are detected by the combination of detection signals outputted from each of the detection switches, number of detection switches may be increased as the number of embroidery frame types are increased. However, such arrangement requires the additional space for providing the detections switches.